Under EU261, Ryanair will also reimburse any reasonable out of pocket expenses incurred by customers as a result of these flight cancellations, subject to receiving an EU261 expense claim form from customers supported by original receipts.’

The Civil Aviation Authority (CAA), which on Thursday accused the Dublin-based carrier of ‘not complying with the law’ over its handling of the fiasco, claimed the airline had ‘capitulated’ after enforcement action was launched.

It had accused Ryanair of not telling passengers that under EU261 rules they were entitled to be re-routed by another carrier.

Ryanair’s offer to passengers features several conditions, including assessing the cost of flights on other airlines ‘on a case by case basis’ before bookings are made.

If there is no Ryanair flight available they will buy seats with rivals including easyJet, Norwegian Air, Jet2, Vueling Aer Lingus.

They will ‘reimburse any reasonable out of pocket expenses’ incurred as a result of their cancellation.

Ryanair’s official spokesman Kenny Jacobs said: ‘We apologise again sincerely for the disruption and inconvenience our rostering failure has caused some of our customers’.

Alex Neill, a managing director at consumer group Which?, said passengers face a ‘potential minefield’ to reach their destination, describing the process as ‘convoluted’.

He added: ‘It still smacks of a lingering reluctance to do the right thing.’

The advert promising a great deal on one million seats on 900 routes until February was sent out to customers today including many left reeling after their flights axed in the same period.

Some joked that buying tickets would simply mean putting a ‘tenner down the drain’.

Ryanair’s decision to launch a £9.99 per-seat mega sale today has sparked incredulous fury among customers caught up in the cancellation crisis

Paul Reynolds‏ tweeted under the advert: ‘Will there be any planes attached to those seats by the way?’, Clive Darken‏ wrote: ‘Can I cancel before I buy???’ and Brodie Agnew‏ asked: ‘How much extra do I have to pay for a plane and a pilot?’.

In the face of a Twitter storm Ryanair’s social media team retained a sense of humour and responded: ‘No worries, that’s been taken care of, so our aircraft and pilot are included in the price’.

Today even Gerald Ratner called on Michael O’Leary to quit and said Ryanair is a ‘joke too far’.

In addition, the Dublin-based carrier must commit to helping passengers who chose an unsuitable option as a result of being misled.

Experts have said that the cancellation crisis could be its ‘Ratner moment’ – a reference to Gerald Ratner’s infamous description of one of the products made by his family jewellery firm as ‘total crap’.

The mega sale has sparked a huge reaction on Twitter, which victims of the cancellation crisis have described as ‘salt in the wound’ and ‘disgusting’

And today it emerged the man himself agrees and told The Times: ‘I think that he (Michael O’Leary) should resign like I did’ – but added: ‘Ryanair is not about to go the way of Ratners’.

Passengers have threatened to boycott the airline after the latest wave of cancellations.

Customers bombarded the firm with complaints following Wednesday’s decisions to cancel flights for another 400,000 passengers over the winter.

A day after Ryanair was accused of ‘cancelling Christmas’ by wrecking more people’s travel plans, passengers using the hashtag #boycottRyanair vowed on Twitter to never fly with the airline again.

Peter Bond wrote ‘#Ryanair what a complete and utter shambles of a company. Not fit for purpose. I’ll never use them #boycottRyanair’.

It comes after the regulator accused the airline of ‘not complying with the law’ over its handling of the fiasco.

CAA chief executive Andrew Haines said he was ‘furious’ after Ryanair cancelled an extra 18,000 flights for the winter season on Wednesday – a move that will hit 400,000 customers.

‘They are not making it clear to people their entitlement,’ Mr Haines told BBC Radio 4’s Today programme.

‘If they follow through on what they are saying, then they would be breaking the law.’

But the CAA said today it would not ‘speculate’ on the action it would take if Ryanair misses the 5pm deadline.

Ryanair boss Michael O’Leary has been told he has until 5pm today to sort out compensation for hundreds of thousands of travellers

Gerald Ratner’s business life fell apart in 1991 (pictured) when he admitted selling ‘crap’ in his high street jewellery shops – many have said Ryanair has had its Ratner moment and the man himself agrees

The Civil Aviation Authority (CAA) has also instructed the budget airline to tell passengers they are entitled to be re-routed by a rival carrier

The airline has been forced to cancel thousands of flights leaving passengers stranded

A Ryanair internal memo allegedly instructed call centre staff to offer flights with other carriers – provided the price ‘does not exceed three times the value of the original Ryanair fare’.

The document, unearthed by ITV News, was criticised by consumer group Which?.

Managing director Alex Neill said: ‘Ryanair appears to be plucking figures out of thin air as there is no legal basis for the arbitrary figure they’ve set.

‘The law says passengers must be rerouted and there’s no specified limit on cost. This yet again highlights the importance of the action which the Civil Aviation Authority has started.

‘It must force Ryanair to immediately change its behaviour and comply with the law.’

A Ryanair spokesman said: ‘We will be meeting with the CAA and will comply fully with whatever requirements they ask us to.’

He added: ‘Ryanair tries to accommodate such reasonable rerouting requests using a guideline (only) of three-times the original airfare.

‘This compares favourably with Easyjet’s stated policy, which limits the cost of ‘alternative transport’ to be ‘within the price range you paid for your original return flight or as close as possible’.

‘British Airways’ stated policy says only that its disrupted customers will be booked ‘onto another British Airways flight’ with no reference to alternative transport (see attached).

‘Ryanair respectfully calls on the CAA to explain what enforcement action it took against British Airways when it suffered a computer systems meltdown at Heathrow on the May Bank Holiday weekend earlier this year.’

The latest round of cancellations includes several popular routes used by British travellers, such as Stansted to Edinburgh and Glasgow, Gatwick to Belfast, Newcastle to Faro, and Glasgow to Las Palmas.

It adds to mounting anger against Ryanair, which was already coming under heavy fire after cancelling up to 50 flights a day earlier this month.

Ryanair says the cancellations were brought about because of an error with pilot holiday rosters.

Some internet wags have lampooned the airline’s cancellation crisis in a series of memes – and Mr O’Leary has been accused of ruining Christmas

Passengers have expressed their frustration with the airline, with many left out of pocket due to a lack of alternative flights and accommodation bookings they can no longer use.

Revolt of the Ryanair pilots as they condemn ‘disresptful’ O’Leary

Ryanair is facing a revolt by its own pilots which threatens to cause even more chaos for passengers.

Furious crew at 60 airports across Europe signed a letter condemning the behaviour of their beleaguered chief executive Michael O’Leary for showing them and their passengers ‘disrespect’ over the cancelled flights fiasco.

In the bombshell letter, the pilots warned there would be no end to the disruption unless their working conditions improve.

They said the crisis would continue unless bosses showed a ‘different management attitude and mindset than the ones that created the problems in the first place’.

Mr Haines said airline passengers are ‘well-protected by the law’.

He went on: ‘They are entitled to compensation and if there is a cancellation, they are entitled to be re-routed by other airlines.

‘The chief executive of Ryanair (Michael O’Leary) has gone on record and said he is not going to do that. He then issued a clarification.

‘But yesterday when they announced 18,000 further cancellations, they failed to follow through on that.

‘We are furious they are not complying with the law and they are not giving customers what they are entitled to.’

The regulator asked for a meeting with the airline as part of a consultation that will last at least seven days and could take legal action for breaching consumer protection laws.

It says Ryanair has falsely claimed it did not have to re-route passengers on other airlines, particularly when there are no other services available.

The CAA also accused the airline of stopping short of providing details on its obligations to refund additional expenses incurred by passengers as a result of cancellations including for meals, hotels and transfer costs.

It enforces consumer rights for passengers on UK flights under the Enterprise Act, meaning it could take Ryanair to court, where it would face being fined.

However, it has no powers to stop the airline from operating in the UK on the grounds of how it treats passengers.

Ryanair’s operating licence is handled by the Irish Aviation Authority.

The airline said the latest reduction in its schedule will ‘eliminate all risk of further flight cancellations’.

Hayley Ruane-Musgrave, right, and Claire Harpur, left, were due to fly to the Canary Islands with their families this Christmas

Best friends Hayley Ruane-Musgrave and Claire Harpur were due to fly to the Canary Islands with their families this Christmas.

But the pair are ‘devastated’ after Ryanair cancelled their flights and now fear they will have to cancel their holidays altogether.

They were due to stay at Caleta De Fuste on Fuerteventura, but they received a text on Wednesday night from Ryanair that read: ‘Please see your email regarding your Ryanair flight.’

After receiving no emails they phoned Sunmaster, the package holiday company which organised their trips, and were told their Ryanair flights had been cancelled.

Initially they were told they would receive a refund, but were later advised to pay an extra £375 to re-book. However, yesterday the prices went up to £505 per family, which they cannot afford.

For 34-year-old Mrs Ruane-Musgrave from Warrington, the £2,800 ten-day holiday was supposed to be her first family trip abroad with her husband and four children. ‘I am devastated because the costs are now extortionate,’ she said.

‘It looks like we will have to cancel – unless Ryanair decide to refund us. I can take it on the chin, but we are going to have to sit our children down and tell them we now aren’t going away on holiday anymore.’

She described the airline company’s refund voucher offer as ‘disgusting and not compensation’. She added: ‘They are just handing out £40 vouchers thinking it will make everything all right. I wouldn’t use the company ever again.’

Mrs Harpur, 34, who lives opposite, was due to join Mrs Ruane-Musgrave with her four children and husband. She booked through the same tour company, but expected to stay for 12 nights instead, costing her £3,000 upfront.

The care worker said: ‘They tried telling us it would cost us an extra £375 to re-book flights and they would keep that for us until [Thursday] until we made our minds up and now it’s gone up to £505 per family. We’ve contacted SunMaster and Ryanair – but they’re just not helping us.’

A Ryanair spokesman said: ‘These customers have been notified via the email provided at the time of booking, and advised of their options, including a full refund or a move (free of charge) to an alternative flight. No requests or contact has been received from these customers. Ryanair continues to operate our Manchester-Fuerteventura route twice weekly (Mondays and Fridays), plus some additional dates over Christmas’.